Internal combustion engines combust an air/fuel mixture within cylinders to drive pistons that rotatably turn a crankshaft to generate drive torque. Abnormal combustion of the air/fuel mixture can cause vibration of the engine (e.g., seismic waves through the engine structure), which is known as “knock.” There are two primary types of engine knock: (1) end-gas auto ignition (also known as “spark knock”) and (2) low speed pre-ignition (LSPI) knock (also known as “mega knock”). LSPI knock refers to a stochastic, abnormal start of combustion prior to spark discharge. Specifically, oil ingestion or chemical pre-reactions due to time, pressure, and temperature may cause auto-ignition, which creates pressure waves that collide causing knock.
LSPI knock is often orders of magnitude higher than spark knock. A typical knock control strategy is spark retardation. This control strategy, however, is not effective against LSPI knock and is actually detrimental in mitigating LSPI knock. This is because during LSPI knock, combustion has already been initiated prior to the spark discharge, and thus retardation of the spark timing provides the cylinder charge even more time for auto-ignition to occur. Accordingly, while such knock detection and control systems work for their intended purpose, there remains a need for improvement in the relevant art.